The present invention relates to a vehicle seat and more particularly, relates to a vehicle seat intended for use in a motor vehicle such as a motor car.
The present invention relates to a vehicle seat and more particularly, relates to a vehicle seat intended for use in a motor vehicle such as a motor car.
It has been appreciated that if a motor vehicle, such as a motor car, is involved in a rear-end collision or rear impactxe2x80x94that is to say if a following vehicle runs into the back of the carxe2x80x94the occupants of the struck car often suffer from neck injuries.
It is to be understood that during a rear-end collision of this type, the vehicle that is struck is subjected to a forward acceleration. This imparts a forward acceleration to the seats of the vehicle. The squab and the back of each occupied seat engage the posterior and torso of the occupant of the seat and impart a substantial acceleration to the posterior and torso of the occupant. However, no corresponding acceleration is immediately imparted to the head of the occupant. The head is a part of the body that has substantial mass, and consequently the head has substantial inertia.
Thus, while the posterior and torso of the occupant of the vehicle are accelerated forwardly as a result of the rear-end collision, the head of the occupant of the vehicle initially remains stationary. This causes the neck initially to adopt a xe2x80x9cSxe2x80x9d-shaped configuration as the lower part of the neck moves forwardly, while remaining vertical, and the upper part of the neck remains in its initial position. Subsequently, the head begins to rotate, and the neck then occupies a curved configuration. The head subsequently moves forwardly. Research has shown that xe2x80x9cwhiplashxe2x80x9d injuries may occur when the neck adopts the xe2x80x9cSxe2x80x9d-shaped configuration, if the head is moving, relative to the torso, at a substantial speed.
The present invention seeks to provide an improved vehicle seat in which the risk of xe2x80x9cwhiplashxe2x80x9d injuries occurring to the occupant of the seat during a rear-end collision are reduced.
According to this invention there is provided a vehicle seat comprising a squab and a back, the back being mounted for pivotal movement relative to the squab of the seat incorporating energy absorbing force limiter arrangement for absorbing energy as the back of the seat moves rearwardly when subjected to a force from the torso of an occupant of the seat if a vehicle in which the seat is mounted is involved in a rear impact, the energy absorbing force limiter arrangement being configured so that the energy absorption of the force limiter arrangement is low at a low energy rear impact and high at a high energy rear impact.
Preferably the back of the seat is mounted, relative to the squab, to move pivotally relative to the squab, the force limiter arrangement being configured to provide a first resistive force resisting the pivotal movement during a first predetermined pivotal movement of the back of the seat, and a second resistive force during the subsequent pivotal movement of the back of the seat, the force limiter arrangement being configured so that the energy absorption during the first predetermined pivotal movement is low at low energy rear impact and high at high energy rear impact.
It is envisaged that in use of the seat of this type, in the event that low energy rear impact occurs, the seat back may move rearwardly, with relatively low energy absorption, during the first predetermined movement. During this movement the head of the seat occupant may engage the head rest. During a subsequent pivotal movement of the back rest, both the head and torso will be subjected to a high force limiting effect. Because the head is engaged by the head rest, the head and torso are both subjected to the same force limiting effect and there is only a minimal risk of injury occurring.
Conveniently the energy absorbing force limiter arrangement comprises elements to provide the first resistive force that include an energy absorbing force limiter and a damped spring.
Preferably the energy absorbing force limiter and the damped spring are connected in series between the back of the seat and an element mounted on the squab of the seat.
Advantageously the damped spring comprises a spring connected in parallel with a fluid-filled cylinder containing a double acting piston, the opposed ends of the cylinder being inter-connected by a parallel connection of a non-return valve and a constriction.
Advantageously the said element mounted on the squab of the seat is pivotally mounted on the squab of the seat and a force limiting device is connected to said pivotally mounted element to absorb energy as the pivotally mounted element moves.
In one embodiment the energy absorbing force limiter arrangement includes a frame present within the back of the set adapted to deform when subjected to a predetermined force.
In a preferred embodiment the energy absorbing force limiter comprises an energy absorbing force limiting device to provide said second resistive force during the second subsequent pivotal movement.
Conveniently the back of the seat is mounted for pivotal movement between predetermined limits relative to a support, the support being pivotally mounted to the squab of the seat, the energy absorbing force limiting device being positioned to absorb energy during pivotal movement of said support.
According to another aspect of this invention there is provided a vehicle seat comprising a squab, a back being mounted for pivotal movement relative to said squab to effect a first predetermined pivotal movement, and a second subsequent predetermined pivotal movement, and a force limiter arrangement for providing a resistive force for resisting the first pivotal movement and the second pivotal movement, the force limiter arrangement being configured to provide a low resistive force during the first pivotal movement in a low energy impact and a high resistive force during the first pivotal movement in a high energy impact, and for providing a high resistive force during the second pivotal movement of each of a low energy impact and a high energy impact.
Advantageously the force limiter arrangement comprises a first energy absorbing force limiting device to provide the resistive force during the first predetermined pivotal movement, and a second force limiting device to provide the resistive force during the second pivotal movement.
Conveniently the first energy absorbing force limiting device comprises an force limiter and a damped spring, the force limiter and damped spring being connected between the back of the seat and the squab of the seat.